The tW process interferes with top quark pair production (\(\mathrm {t}\overline{\mathrm {t}}\) ) at NLO in QCD. In this analysis, two schemes are defined to treat this interference: diagram removal (DR), in which all doubly resonant diagrams are removed from the matrix element (ME) calculation, and diagram subtraction (DS), in which a gauge invariant term is introduced in the ME calculation that locally cancels the doubly resonant diagrams. The tW production cross section is computed at approximate next-to-next-to-leading order (NNLO). The corresponding theoretical prediction for the tW cross section in pp collisions at \(\sqrt{s} = 13\)  TeV, assuming a top quark mass (\(m_{\mathrm {t}}\) ) of 172.5 GeV [1]}, is \(\sigma ^{\mathrm {SM}}_{\mathrm {tW}} = 71.7 \pm 1.8 (\mathrm {scale}) \pm 3.4 (\mathrm {PDF}) \ \mathrm {pb.}\)
